a(n) = a(n-4) + a(n-3) + a(n-2) + a(n-1) + (n-5).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =4a(5) =8a(6) =16a(7) =32a(8) =64a(9) =125a(10) =243a(11) =471a(12) =911a(13) =1759a(14) =3394a(15) =6546a(16) =12622a(17) =24334a(18) =46910a(19) =90427a(20) =174309a(21) =335997a(22) =647661a(23) =1248413a(24) =2406400a(25) =4638492a(26) =8940988a(27) =17234316a(28) =33220220a(29) =64034041